Design and analysis of front spar wing-tip segment for a small transport aircraft

Abstract

Structural safety is an important aspect of the design of airframes. The spar is one of the critical structural elements of the airframe. The wing is subjected to bending due to shear loads caused by aerodynamic pressure, it undergoes compression and tension. This paper deals with the design of a segment of the front spar spanning from wing mid-section to the tip end on strength of materials approach. The load on the spar segment will be considered from a global wing stress analysis. Typical elliptical load distribution on the transport aircraft is considered. The wing is a statically indeterminate structure, the cross-section of a typical wing section is assumed and the maximum bending moment load case I s considered for wing stress analysis. The spar tip segment will be designed so it does not suffer any permanent deformation under the design limit load. Global finite element stress analysis will be carried out to check the validation of the design. Usually, a thumb rule assumption is made that spar takes a definite percentage of load but in this paper, the load acting on the spar is just not a mere assumption but a different approach called the ‘W/I method’. The spar tip segment is designed based on the load magnitude and distribution using the strength of materials approach.